Traditionally jets run on high-octane oil byproducts. Oil is an
"omnivorous" diet of sorts, in so much as it is composed of a
hydrocarbon stew of decomposed plants and animals, though its primary
contributors are prehistoric plants and bacteria.

In March and April, researchers at NASA Dryden Flight
Research Center in California test biofuel made of chicken and
beef tallow (waste fat) in the engine of a DC-8 airplane. NASA hopes that
the study makes people realize that biofuels don't have to
come from plant sources necessarily -- they can also come from flesh.

Writes the agency's press release:

"Renewable" means that the fuel source isn't some form
of fossil fuel. The source could be algae, a plant such as jatropha, or even
rendered animal fat.

To test the new animal-based biofuel, the researchers ran one engine burning
Jet Propellant 8, or JP-8, fuel, which is very similar to the industry standard
Jet-A fuel used in commercial aircraft. They ran a second engine on a
50-50 blend of JP-8 and Hydrotreated Renewable Jet Fuel, or HRJ -- the
animal-based biofuel. And a third engine ran on pure HRJ.

The test was dubbed the Alternative Aviation Fuels Experiment, or AAFEX.

The key goal was to measure the amount of emissions put off by a jet running on
biofuel versus one on fossil fuel -- something that had never been done before.

What they found was that the biofuel-powered engine produced much lower sulfate, organic aerosol, and hazardous emissions. It
also produced 90 percent less black carbon emissions at idle and 60 percent
less at a takeoff level of thrust. Emissions of nitrogen oxides,
commonly known as NOx, were also much lower. NOx is a key component of smog and
can directly trigger asthma attacks and respiratory problems in humans.

Ruben Del Rosario, a NASA manager of the Subsonic Fixed
Wing Project at the Glenn Research Center in
Ohio, states, "The test results seem to support the idea that biofuels for
jet engines are indeed cleaner-burning, and release fewer pollutants into the
air. That benefits us all."

The testing was quite open with 17 government agencies, universities, and
industry players participating in the test and data analysis. The tests
were funded by the NASA's Aeronautics
Research Mission Directorate in Washington.

The tests are somewhat of a sequel to a series
of tests in 2009 in which engineers and researchers evaluated
the performance of engines running on "synthetic fuels", like liquefied
coal and natural gas. Researchers in that test also found that emissions
were significantly reduced over traditional fossil fuels.